Magnetic and fluorescent core-shell nanoparticles for ratiometric pH sensing

Enhanced theranostic efficacy of epirubicin-loaded SPION@MSN through co-delivery of an anti-miR-21-expressing plasmid and ZIF-8 hybridization to target colon adenocarcinoma

Using targeted drug delivery systems has emerged as a promising approach to increase the efficacy of chemotherapy, particularly in combination with gene therapy. The overexpression of miR-21 plays a crucial role in colorectal cancer (CRC) progression, and targeted inhibition of miR-21 offers significant potential for enhancing CRC chemotherapy outcomes. In this study, a theranostic system based on mesoporous silica and superparamagnetic iron oxide nanoparticles (SPION@MSNs) was synthesized as a core-shell structure. After loading epirubicin (EPI) in the open pores of MSN, the plasmid expressing anti-miR-21 (pDNA) covered the outer surface with the help of a ZIF-8 (zeolitic imidazolate framework-8) film. Afterward, polyethylene glycol (PEG) and AS1411 aptamer were conjugated to the surface to improve the protective, biocompatibility, and targeting abilities of the nanocarrier. Moreover, the physicochemical characteristics as well as the loading capacity and release profile of EPI and pDNA were fully evaluated. The uptake of the nanoparticles by CRC and normal cell lines in addition to the anticancer effects related to targeted combinational therapy were investigated in vitro. Finally, in vivo tests were performed on BALB/c mice bearing colorectal tumors to evaluate the effectiveness of the targeted nanoparticles, their possible side effects, and also their application in fluorescence and magnetic imaging in vivo. The successful synthesis of SPION@MSN-EPI/pDNA-ZIF-8-PEG-Apt nanoparticles (∼68 nm) and good loading efficiency and controlled release of EPI and pDNA were confirmed. Moreover, hemolysis and gel retardation assays demonstrated the biocompatibility and plasmid protection. Cellular uptake and expression of copGFP illustrated selective entry and transient transfection of targeted nanoparticles, consistent with the cytotoxicity results that indicated the synergistic effects of chemo-gene therapy. The results of animal studies proved the high antitumor efficiency of targeted nanoparticles with minimal tissue damage, which was in line with fluorescence and magnetic imaging results. The novel synthesized nanoparticles containing SPION@MSN-ZIF-8 were suitable for CRC theranostics, and the combined approach of chemo-gene therapy suppressed the tumor more effectively.

Core-Shell Magnetic Imprinted Polymers for the Recognition of FLAG-Tagpeptide

FLAG^® tag (DYKDDDDK) is a small epitope peptide employed for the purification of recombinant proteins such as immunoglobulins, cytokines, and gene regulatory proteins. It provides superior purity and recoveries of fused target proteins when compared to the commonly used His-tag. Nevertheless, the immunoaffinity-based adsorbents required for their isolation are far more expensive than the ligand-based affinity resin used in combination with the His-tag. In order to overcome this limitation we report herein the development of molecularly imprinted polymers (MIPs) selective to the FLAG^® tag. The polymers were prepared by the epitope imprinting approach using a four amino acids peptide, DYKD, including part of the FLAG^® sequence as template molecule. Different kinds of magnetic polymers were synthesised in aqueous and organic media also using different sizes of magnetite core nanoparticles. The synthesised polymers were used as solid phase extraction materials with excellent recoveries and high specificity for both peptides. The magnetic properties of the polymers confer a new, effective, simple, and fast method in the purification using FLAG^® tag.

Synthesis of a thermoresponsive crosslinked MEO2MA polymer coating on microclusters of iron oxide nanoparticles

Encapsulation of magnetic nanoparticles (MNPs) of iron (II, III) oxide (Fe3O4) with a thermopolymeric shell of a crosslinked poly(2-(2-methoxyethoxy)ethyl methacrylate) P(MEO2MA) is successfully developed. Magnetic aggregates of large size, around 150-200 nm are obtained during the functionalization of the iron oxide NPs with vinyl groups by using 3-butenoic acid in the presence of a water soluble azo-initiator and a surfactant, at 70 °C. These polymerizable groups provide a covalent attachment of the P(MEO2MA) shell on the surface of the MNPs while a crosslinked network is achieved by including tetraethylene glycol dimethacrylate in the precipitation polymerization synthesis. Temperature control is used to modulate the swelling-to-collapse transition volume until a maximum of around 21:1 ratio between the expanded: shrunk states (from 364 to 144 nm in diameter) between 9 and 49 °C. The hybrid Fe3O4@P(MEO2MA) microgel exhibits a lower critical solution temperature of 21.9 °C below the corresponding value for P(MEO2MA) (bulk, 26 °C). The MEO2MA coating performance in the hybrid microgel is characterized by dynamic light scattering and transmission electron microscopy. The content of preformed MNPs [up to 30.2 (wt%) vs. microgel] was established by thermogravimetric analysis while magnetic properties by vibrating sample magnetometry.

Synthesis of Fe3O4@Gd2O3:Tb3+@SiOx multifunctional nanoparticles and their luminescent, magnetic and hyperthermia properties

Multifunctional Fe₃O₄@Gd₂O₃:Tb³⁺@SiOx nanoparticles were successfully synthesized by co-precipitation and polyol methods. The synthesized nanoparticles were composed by cubic phase as core of Fe₃O₄ and Gd₂O₃:Tb³⁺ and the shell of amorphous SiOx. The composites exhibited a spherical shape with a diameter of 10-15 nm and highly uniform dispersion. They showed not only excellent fluorescence under excitation at a wavelength of 278 nm, but also strong magnetic responsiveness (M_S = 24.040 emu g^-1). The results of magnetic resonance imaging in vitro (r₁ = 6.00 mm^-1 s^-1, r₂ = 63.95 mm^-1 s^-1) showed that the samples could be used as T₁-positive and T₂-negative contrast agents. In addition, it was found that Fe₃O₄@Gd₂O₃:Tb³⁺@SiOx attains hyperthermia temperature (43 °C) in 90 s under the alternating current magnetic field, and their specific absorption rate (229.9 w g^-1) was higher than that of Fe₃O₄ (183.92 w g^-1). Hence, the multifunctional nanoparticle could be used for the diagnosis and therapy of cancer.

Anti-inflammatory Nanoparticle for Prevention of Atherosclerotic Vascular Diseases

Recent technical innovation has enabled chemical modifications of small materials and various kinds of nanoparticles have been created. In clinical settings, nanoparticle-mediated drug delivery systems have been used in the field of cancer care to deliver therapeutic agents specifically to cancer tissues and to enhance the efficacy of drugs by gradually releasing their contents. In addition, nanotechnology has enabled the visualization of various molecular processes by targeting proteinases or inflammation. Nanoparticles that consist of poly (lactic-co-glycolic) acid (PLGA) deliver therapeutic agents to monocytes/macrophages and function as anti-inflammatory nanoparticles in combination with statins, angiotensin receptor antagonists, or agonists of peroxisome proliferator-activated receptor-γ (PPARγ). PLGA nanoparticle-mediated delivery of pitavastatin has been shown to prevent inflammation and ameliorated features associated with plaque ruptures in hyperlipidemic mice. PLGA nanoparticles were also delivered to tissues with increased vascular permeability and nanoparticles incorporating pitavastatin, injected intramuscularly, were retained in ischemic tissues and induced therapeutic arteriogenesis. This resulted in attenuation of hind limb ischemia. Ex vivo treatment of vein grafts with imatinib nanoparticles before graft implantation has been demonstrated to inhibit lesion development. These results suggest that nanoparticle-mediated drug delivery system can be a promising strategy as a next generation therapy for atherosclerotic vascular diseases.

A plug-and-play ratiometric pH-sensing nanoprobe for high-throughput investigation of endosomal escape

An important aspect in the design of nanomaterials for delivery is an understanding of its uptake and ultimate release to the cytosol of target cells. Real-time chemical sensing using a nanoparticle-based platform affords exquisite insight into the trafficking of materials and their cargo into cells. This versatile and tunable technology provides a powerful tool to probe the mechanism of cellular entry and cytosolic delivery of a variety of materials, allowing for a simple and convenient means to screen materials towards efficient delivery of therapeutics such as nucleic acids.

Novel silica surface charge density mediated control of the optical properties of embedded optically active materials and its application for fiber optic pH sensing at elevated temperatures

Silica and silica incorporated nanocomposite materials have been extensively studied for a wide range of applications. Here we demonstrate an intriguing optical effect of silica that, depending on the solution pH, amplifies or attenuates the optical absorption of a variety of embedded optically active materials with very distinct properties, such as plasmonic Au nanoparticles, non-plasmonic Pt nanoparticles, and the organic dye rhodamine B (not a pH indicator), coated on an optical fiber. Interestingly, the observed optical response to varying pH appears to follow the surface charge density of the silica matrix for all the three different optically active materials. To the best of our knowledge, this optical effect has not been previously reported and it appears universal in that it is likely that any optically active material can be incorporated into the silica matrix to respond to solution pH or surface charge density variations. A direct application of this effect is for optical pH sensing which has very attractive features that can enable minimally invasive, remote, real time and continuous distributed pH monitoring. Particularly, as demonstrated here, using highly stable metal nanoparticles embedded in an inorganic silica matrix can significantly improve the capability of pH sensing in extremely harsh environments which is of increasing importance for applications in unconventional oil and gas resource recovery, carbon sequestration, water quality monitoring, etc. Our approach opens a pathway towards possible future development of robust optical pH sensors for the most demanding environmental conditions. The newly discovered optical effect of silica also offers the potential for control of the optical properties of optically active materials for a range of other potential applications such as electrochromic devices.

Development of organically modified silica nanoparticles for monitoring the intracellular level of oxygen using a frequency-domain FLIM platform

The dynamic quenching of luminescence derived from Ru(dpp₃)²⁺-doped ORMOSIL nanoparticles is used for monitoring of the intracellular oxygen concentration.

Magnetic particle hyperthermia--a promising tumour therapy?

We present a critical review of the state of the art of magnetic particle hyperthermia (MPH) as a minimal invasive tumour therapy. Magnetic principles of heating mechanisms are discussed with respect to the optimum choice of nanoparticle properties. In particular, the relation between superparamagnetic and ferrimagnetic single domain nanoparticles is clarified in order to choose the appropriate particle size distribution and the role of particle mobility for the relaxation path is discussed. Knowledge of the effect of particle properties for achieving high specific heating power provides necessary guidelines for development of nanoparticles tailored for tumour therapy. Nanoscale heat transfer processes are discussed with respect to the achievable temperature increase in cancer cells. The need to realize a well-controlled temperature distribution in tumour tissue represents the most serious problem of MPH, at present. Visionary concepts of particle administration, in particular by means of antibody targeting, are far from clinical practice, yet. On the basis of current knowledge of treating cancer by thermal damaging, this article elucidates possibilities, prospects, and challenges for establishment of MPH as a standard medical procedure.

Silica-based nanocomposites via reverse microemulsions: classifications, preparations, and applications

Silica-based nanocomposites with amorphous silica as the matrix or carrier along with a functional component have been extensively investigated. These nanocomposites combine the advantages of both silica and the functional components, demonstrating great potential for various applications. To synthesize such composites, one of the most frequently used methods is reverse microemulsion due to its convenient control over the size, shape, and structures. The structures of the composites have a decisive significance for their properties and applications. In this review, we tried to categorize the silica-based nanocomposites via reverse microemulsions based on their structures, discussed the syntheses individually for each structure, summarized their applications, and made some perspectives based on the current progress of this field.

Bifunctional nanoparticles with magnetism and NIR fluorescence: controlled synthesis from combination of AGET ATRP and 'click' reaction

In this work, bifunctional nanoparticles (NPs) capable of emitting near infrared (NIR) fluorescence and generating superparamagnetism under an external magnetic field were prepared by combination of 'click' reaction and surface-initiated activators generated by electron transfer for atom transfer radical polymerization (AGET ATRP) of water-soluble poly(ethylene glycol) monomethyl ether methacrylate (PEGMA) and glycidyl methacrylate (GMA) using biocompatible iron as the catalyst on the surface of silica-coated iron oxide (Fe3O4@SiO2) NPs. The nanosized Fe3O4@SiO2@PPEGMA-co-PGMA@N3 was prepared through AGET ATRP and alkynyl bearing NIR dye was also prepared; afterwards they were integrated together by 'click' reaction. The different stages of surface modification were approved by employing different characterization techniques such as TEM, XRD, XPS, VSM and FT-IR, and the properties of the final NPs were thoroughly studied. Their suitability as dual model imaging agents for magnetic resonance (MR) and fluorescence imaging was investigated, indicating them to be a competitive candidate for imaging contrast agents.

Silica nanoparticles for cell imaging and intracellular sensing

There is increasing interest in the use of nanoparticles (NPs) for biomedical applications. In particular, nanobiophotonic approaches using fluorescence offers the potential of high sensitivity and selectivity in applications such as cell imaging and intracellular sensing. In this review, we focus primarily on the use of fluorescent silica NPs for these applications and, in so doing, aim to enhance and complement the key recent review articles on these topics. We summarize the main synthetic approaches, namely the Stöber and microemulsion processes, and, in this context, we deal with issues in relation to both covalent and physical incorporation of different types of dyes in the particles. The important issue of NP functionalization for conjugation to biomolecules is discussed and strategies published in the recent literature are highlighted and evaluated. We cite recent examples of the use of fluorescent silica NPs for cell imaging in the areas of cancer, stem cell and infectious disease research, and we review the current literature on the use of silica NPs for intracellular sensing of oxygen, pH and ionic species. We include a short final section which seeks to identify the main challenges and obstacles in relation to the potential widespread use of these particles for in vivo diagnostics and therapeutics.

Superparamagnetic iron oxide based nanoprobes for imaging and theranostics

The need to target, deliver and subsequently evaluate the efficacy of therapeutics in the treatment of a disease has provided added impetus in developing novel and highly efficient contrast agents. Superparamagnetic iron oxide nanoparticles (SPIONs) have offered tremendous potential in designing advanced magnetic resonance imaging (MRI) diagnostic agents, due to their unique physicochemical properties. There has been tremendous effort devoted in the recent past in developing synthetic methodologies through which their size, hydrodynamic radii, chemical composition and morphologies could be tailored at the nanoscale. This enables one to fine tune their magnetic behavior, and thus their MRI response. While novel synthetic strategies are being assembled for directing SPIONs to the diseased site as well as imparting them stealth and biocompatibility, it is also essential to evaluate their biological toxicological profiles. This review highlights recent advances that have been made in the synthesis of SPIONs, subsequent functionalization with desired entities, and a discussion on their use as MRI contrast agents in cardiovascular research.